A Blog/Weblog Client software will lets you post to your blog via XML-RPC. You don’t need to be online to use this software, this software will run on your local machine (desktop). There are many software available today.
If you’re searching for a free weblog client software , ScribeFire is worth a look. ScribeFire is a full-featured blog editor that integrates with your firefox browser and lets you easily post to your blog.